High tension electric distributing system and apparatus



Jan. 2, 1934. G. A. BURNHAM 1,941,453

HIGH TENSION ELECTRIC DISTRIBUTING SYSTEM AND APPARATUS Filed Feb. 6, 1928 ,fnverzi'oit Patented Jan. 2, 1934 UNITED STATES HIGH TENSION 1,941,483 7 ELECTRIC DISTRIBUTING SYSTEM AND APPARATUS George A. Burnham, Saugus, Mass., assignor to Oondit Electrical Manufacturing Corporation,

South Boston, chusetts Mass, a corporation of Massa- Application February 6, 1928. Serial No.- 252,185

8 Claim.

This invention relates to high tension electric distributing and switching systems and apparatus wherein the high tension buses, usually extended directly from the generators, are contained in ducts and are extended immediately above or beside oil immersed switches which are connected with the buses and also with branch lines which they control. When oil switches are opened under heavy loads or under a short cir- 10 cuit, heated oil and flame are frequently expelled from the switch casings. If the heated vapor or flame comes in contact with the high tension buses, it forms a sufliciently low conducting path between them to cause a disastrous 16 are to form. Since the buses usually are directly connected with the generators without interposed overload circuit breakers therein; there is no way of quenching the arc and removing the short circuit from the buses. The arc can there- 20 upon continue indefinitely and cause great damage to the station and cause a loss of service extending over many hours. As a consequence, the buses are usually enclosed in the aforesaid ducts to shield them from contact with conducting gases that may be expelled from the switches.

There are a number of types of bus enclosing systems. In one type, the duct in which the bus is contained isv filled with oil which serves not only to shield the bus from contact with gases 80 but also to provide the "insulation for the bus. With this system, however, the duct must be made and kept absolutely oil tight, otherwise the oil will leak out and'remove the insulation from the bus so that a flash over will occur from the bus to the duct, which usually is made of metal. Danger from fire, due to the ignition of the oil in the duct from a possible flash over, is always present. When a flash over occurs large volumes of explosive gases and vapors may be generated;

40 and these may explode and do great damage.

' another type of bus structure the oil is replaced by an insulating compound 'which is poured into the duct while hot,"and .liquid, and

cools 'and solidifies about the bus and thus forms a hard and brittle insulating compound. Danger T of leakage of the insulating compound'is thus obviated but the fire hazard is not greatly reduced. Since the compound is brittle, it has a tendency to crack when subjected to strains and "thusopen up a path for a flash over arc. The

disastrous results.

- In yet another system of bus-structure, the

bus is contained within a duct which contains no especial insulating material, and the duct is arc sets fire. to the compound and it burns, with (Cl. Iva-266) made sufliciently large in cross section to prevent flash over between the bus and the conducting walls of the duct. With this type of structure, it has been found that hot gases discharged from the switch will be forced into the duct through seemingly minute crevices and channels between the walls and cause the formation of an are between the bus and the duct. In some instances, it has been found that the interior walls of the duct and the insulators on which the bus is mounted become coated with carbon expelled from the oil switch and that the carbon provided a conducting path which caused a flash over and the failure of the distribution system.

It is an object of the present invention to provide a distributing and switching system of the general type above set forth which has as one of its cooperating elements a high tension bus structure so arranged that gas and fume expelled from the switch or other oil immersed electrical apparatus, or one containing a combustible medium, can not come in contact with the bus and also so arranged that the troubles and defects of the above enumerated present systems are absent.

It is a further object of the invention to provide a high tension bus or conductor which is electrically and mechanically insulated from surrounding objects by a mobile insulating body consisting of solid, discrete, insulating and noncombustible particles, as sand, and a liquid'insulating medium as oil contained in the voidsbetween the sand. x

Another object of the invention is the provision of a high tension conductor protected from extraneous influences by a body of sand which contains oil or equivalent liquid which completely fills the voids between the sand particles and thus, in combination with the sand, provides an insulating body of high dielectric strength for the bus.

A further object of the invention is the provision of a high tension conductor insulated by oil, or

some similar insulating medium, contained in a .iluid pervious body which prevents the flow of over, or other cause, the combustion will not be 7 readily propagated away from its initial source but will have a strong tendency to go out.

A further object is generally to improve the construction and operation of electrical distributing and switching systems and apparatus and high tension conductors.

Fig. 1 is a side elevation partly insection of an enclosed high tension distributing and switching system embodying the invention.

Fig. 2 is a perspective view of a bus duct of Fig. 1.

Fig. 3 is a longitudinal sectional elevation similar to Fig. 2 through a bus duct embodying the invention.

Fig. 4 is an enlarged sectional detail of the insulating material embodying the invention and showing the relative positions of the solid and liquid insulating materials.

Fig. 1 illustrates a three-phase high tension distributing and switching apparatus embodying the invention. The oil switches 10, one of which is here shown, are supported on a frame 12 and can be raised and lowered into and out of operative position by mechanism including the lead screw 14. The frame 12 also provides support, above the switch, for a plurality of superposed ducts, or enclosures, 16, 18 and 20 in which are contained high tension conductors, or buses, 22, 24 and 26, each constituting a phase conductor, and supported on suitable insulators 28. Said buses are connected with the switches through conductors 30, one being here shown, which are enclosed in depending ducts 32 and terminate in bushings 34, the lower ends of which are provided with disengageable terminals adapted to engage the terminals 36 of the oil switches. Outgoing cables 38, one of which is here shown, are extended into ducts or pot heads 40, located below the lowermost bus duct 16 and are connected with bushings 42,

the lower ends of which also make a breakable connection with the other terminals 44 of the oil switches. Pots 46 are carried by and surround the oil switch terminals and are adapted to contain oil or other insulating medium in which connection between the bushings of the bus and cable structures are made with the switch terminals so that all high tension conductors are surrounded with an insulating medium.

The bus ducts 16, 18 and 20 can be of any suitable material and nature, and, as here shown, are composed of sheet metal walls 48 having the removable cover 50.

The structure above described is set forth in my copending application Serial No. 239,790, filed December 13, 1927 which has resulted in Patent No. 1,748,060, issued Feb. 25, 1930.

In accordance with the present invention, the high tension bus is electrically insulated from the walls of the enclosing ducts and also against any gases and fumes that may be expelled from the oil switchor result from the combustion of any material adjacent to the bus by an insulating body 52 which fills the duct and in which the bus is embedded. Said insulating body is composed of loose, electrically-insulating non-combustible particles 54 as sand. The voids between the sand particles are completely filled by an insulating liquid, as oil, which excludes air from the insulating body. This composite insulating body has unusual and highly advantageous voids between them are sufliciently small to retain the oil bodies therein so that the oil will not escape even though the duct is fluid perforate, or through accident, has openings formed therein. Consequently, the insulation of the duct will remain unimpaired whereas in a purely oil insulated bus structure, the oil will escape if the bus enclosure becomes leaky.

If a flash-over occurs between the bus and the wall of the enclosing duct, the amount of oil that is acted upon by the flash over are is very small as compared with the volume of oil that can be acted upon in the usual completely oil insulated bus. Therefore, with the present arrangement but a small amount of gases and a small pressure will be generated. If the oil in the voids begins to burn at some place for any reason the flame can not be transmitted readily throughout the oil body. The sand particles not only prevent free fluid communication throughout the duct but they chill the oil and the flame, and cause the flame to go out, so that only the small amount of oil at the source of the flame is consumed and no oil can run into the source of the flame since the sand particles retain the oil in the voids between them.

The insulating body is mobile so that it can flex and bend with any movement of the enclosing duct without impairing the insulation of the bus.

The sand can be any clean, non-conducting sand that is inert to the are, as a quartz sand. The use of quartz is particularly desirable not only by reason of its inertness to the are but also by reason of its high electrical insulation, high thenno-conductivity, and its piezo-electric properties, as well as because of other properties. The size of the sand particles can vary within rather wide limits but preferably should be sufficiently small to maintain the oil in the voids between the particles so that the oil will not run out. Sand particles about mm. thick give good results. The oil prevents the formation of corona between the sand particles and thus improves the insulation provided by the sand body alone.

I claim:

1. The combination of a high tension conductor, and mobile insulating means therefor consisting of a gas-impermeable body of loose solid non-combustible insulating particles surrounding the conductor and a liquid insulating material retained in and filling the voids between said insulating particles.

2. The combination of a high tension conductor, and insulating means therefor consisting of a conductor-enclosure, a liquid insulating medium therein, and a gas-impermeable body of loose solid, non-combustible insulating particles in said enclosure and insulating medium and enclosing said bus, said liquid insulating medium being retained in and filling the voids between said solid insulating particles.

3. The combination of a high tension conductor, an enclosure therefor, a liquid insulating body surrounding said conductor in said enclosure, and means comprising a mass of loose solid discrete insulating non-combustible particles located within and in intimate contact with said liquid body, said liquid body being retained in and filling the voids between said particles.

4. The combination of a high tension conductor, a combustible insulating liquid body surrounding and insulating said conductor, and cooling means comprising a mass of solid, discrete non-combustible insulating particles 10- cated within and in intimate contact with said insulating body which renders dimcult the combustion thereof and which retainssaid body against flow.

5-. The combination of a high tension conductor, and insulating means therefor including a porous homogeneous mobile body of solid, insulating non-combustible material surrounding and enclosing said conductor, and a liquid insulating medium contained within and filling the pores of said body, the pores being so small that the liquid is retained therein against flow.

6. The combination of a high tension conductor, and isolating and electrical insulating means therefor comprising a combustible body of insulating liquid surrounding and insulating said conductor, and a mobile body of quartz particles located within and in intimate contact with said liquid and rendering diflicult the combustion thereof said quartz particles being so small as to retain the liquid within the voids between the'particles against flow.

7. An electrical apparatus comprising one or more members housed within a casing and spaced therefrom, said spaces being subject to electric potential stresses produced by said member or members, there being loose particles of piezoelectric material disposed in said spaces, whereby said members are insulated from the casing and one another, the cavities and air spaces between the particles of the piezo-electric material being filled up with a liquid insulating material,

said particles of piezo-electric material being so small as to retain the liquid within the voids between the particles.

8. An electrical apparatus comprising a casing, one or more members to be insulated from the casing and each other, housed within said casing, the spaces between said casing and member or members, being subject to electric potential stresses, said spaces being'filled with a gas impermeable body of loose particles of a piezoelectric material, the interstices between the particles of the piezo-electric material being filled with an insulating liquid.

GEORGE A. BURNHAM. 

